Esmunyedissa pròstata

La detecció efectiva del càncer de pròstata encara s’esmuny. És l’únic òrgan intern al qual es fan biòpsies a cegues perquè no es disposa de cap eina específica, barata i eficient. La conseqüència d’aquesta situació, la percep el malalt, que, de vegades, ha de sotmetre’s a diverses i molestes proves sense la seguretat d’obtenir un diagnòstic clar. Investigadors de la Universitat de Girona i de Ressonància Girona treballen conjuntament per aportar una solució a aquest problema

L'Aigua al segle XXI

La Universitat de Girona té alguna cosa a dir sobre l’aigua, perquè hi ha diverses persones que s’han especialitzat en el seu coneixement, estudiant-ne el context ambiental, interpretant-ne la gestió o preveient-ne les necessitats actuals i futures. Engega ha reunit uns quants d’aquests investigadors perquè expressin, des de la seva expertesa, el que pensen de l’aigua

Vattimo, estimulant i compromès

Comentari sobre el pensador Gianni Vattimo en motiu del Seminari que ha impartit organitzat per la Càtedra Ferrater Mora de Pensament Contemporani

La Visió d'AQSENSE

Potència i velocitat. Aquests són els atributs amb els quals la premsa alemanya especialitzada en visió artificial ha definit el software de captura de formes que comercialitza AQSENSE, una empresa amb projecció internacional que té la seu al Parc Científic i Tecnològic de Girona

Perfils: Alfons Cornellà

Alfons Cornella és el director i fundador d’Infonomia. Aquest portal s’ha convertit en un centre de coneixement d’avantguarda, especialitzat a proveir d’eines i serveis que estimulin la competitivitat de les petites, mitjanes i grans empreses

UdGExpress

Dues notícies sobre el moviment d'accés obert a la UdG: la incorporació de la Revista de Girona a RACO, i el seminari Els Canvis en la Comunicació Científica: el Moviment d’Accés Obert

Novetats editorials

Novetats editorials de Documenta Universitària i Accent Editorial

Fons d'art

Dues aportacions artístiques a la UdG, una obra de Fita i una altra de Comadira

Ramon Carbó-Dorca: "Per resoldre els problemes bàsics de la ciència, amb un paper i un llapis n'hi ha prou"

Ramon Carbó-Dorca va néixer a Girona un dia de tardor de 1940 en què la ciutat es negava en les aigües dels seus rius. Començar la vida enmig d’una contingència com aquella l’ha dut a pensar —explica— que no paga la pena preocupar-se de segons quines coses. Carbó-Dorca estudia a través de la semblança molecular la relació entre l’estructura i les propietats de les molècules

The relevance of the Laplacian of intracule and extracule density distributions for analyzing electron-electron interactions in molecules

A topological analysis of intracule and extracule densities and their Laplacians computed within the Hartree-Fock approximation is presented. The analysis of the density distributions reveals that among all possible electron-electron interactions in atoms and between atoms in molecules only very few are located rigorously as local maxima. In contrast, they are clearly identified as local minima in the topology of Laplacian maps. The conceptually different interpretation of intracule and extracule maps is also discussed in detail. An application example to the C2H2, C2H4, and C2H6 series of molecules is presented

Determination of vibrational polarizabilities and hyperpolarizabilities using field-induced coordinates

An analytical set of field-induced coordinates is defined and is used to show that the vibrational degrees of freedom required to completely describe nuclear relaxation polarizabilities and hyperpolarizabilities is reduced from 3N-6 to a relatively small number. As this number does not depend upon the size of the molecule, the process provides computational advantages. A method is provided to separate anharmonic contributions from harmonic contributions as well as effective mechanical from electrical anharmonicity. The procedures are illustrated by Hartree-Fock calculations, indicating that anharmonicity can be very important

Treatment of nonlinear optical properties due to large amplitude anharmonic vibrational motions: umbrella motion in NH3

A general reduced dimensionality finite field nuclear relaxation method for calculating vibrational nonlinear optical properties of molecules with large contributions due to anharmonic motions is introduced. In an initial application to the umbrella (inversion) motion of NH3 it is found that difficulties associated with a conventional single well treatment are overcome and that the particular definition of the inversion coordinate is not important. Future applications are described

A comparative analysis of two methods for the calculation of electric-field-induced perturbations to molecular vibration

Two common methods of accounting for electric-field-induced perturbations to molecular vibration are analyzed and compared. The first method is based on a perturbation-theoretic treatment and the second on a finite-field treatment. The relationship between the two, which is not immediately apparent, is made by developing an algebraic formalism for the latter. Some of the higher-order terms in this development are documented here for the first time. As well as considering vibrational dipole polarizabilities and hyperpolarizabilities, we also make mention of the vibrational Stark effec

One- and two-center energy components in the atoms in molecules theory

The energy decomposition scheme proposed in a recent paper has been realized by performing numerical integrations. The sample calculations carried out for some simple molecules show excellent agreement with the chemical picture of molecules, indicating that such an energy decomposition analysis can be useful from the point of view of connecting quantum mechanics with the genuine chemical concepts

How does basis set superposition error change the potential surfaces for hydrogen-bonded dimers?

We describe a simple method to automate the geometric optimization of molecular orbital calculations of supermolecules on potential surfaces that are corrected for basis set superposition error using the counterpoise (CP) method. This method is applied to the H-bonding complexes HF/HCN, HF/H2O, and HCCH/H2O using the 6-31G(d,p) and D95 + + (d,p) basis sets at both the Hartree-Fock and second-order Møller-Plesset levels. We report the interaction energies, geometries, and vibrational frequencies of these complexes on the CP-optimized surfaces; and compare them with similar values calculated using traditional methods, including the (more traditional) single point CP correction. Upon optimization on the CP-corrected surface, the interaction energies become more negative (before vibrational corrections) and the H-bonding stretching vibrations decrease in all cases. The extent of the effects vary from extremely small to quite large depending on the complex and the calculational method. The relative magnitudes of the vibrational corrections cannot be predicted from the H-bond stretching frequencies alone